A technique of using plural receiving apparatuses and plural wireless terminals to determine the position of a wireless terminal is known (for example, refer to Japanese Laid-Open Patent Publication No. 2007-221541). A radio frequency identification (RFID) system is further known in which plural monitoring apparatuses and plural nodes (wireless sensors, etc.) are used (for example, refer to Japanese Laid-Open Patent Publication No. 2010-213278).
Furthermore, according to a known technique, in an ad hoc network, the distance between a mobile terminal apparatus and each base station is estimated based on the hop count of a wireless signal from the mobile terminal apparatus to the base stations, and based on the estimation result, the position of the mobile terminal apparatus is determined (for example, refer to Japanese Laid-Open Patent Publication No. 2006-229845). Sensor networks (wireless sensor networks) are further known in which plural sensor-equipped wireless terminals are interspersed and work in concert to enable environmental and/or physical states to be obtained.
Nonetheless, with the conventional techniques above, distribution of the interspersed nodes is not uniform and if an area without a node is present, a wireless signal may be transmitted by being diverted away from the area. In this case, a problem arises in that the position of the transmission source of the wireless signal cannot be accurately determined.